When any two dissimilar materials are in contact, and an electric current flows from one material to the other, heat energy flows into or out of the junction between the materials. Whether the heat flows in or out depends on the direction of the current flow. This is the well-known Peltier effect. The amount of heat flow is proportional to the amount of current and is also proportional to the Peltier coefficients of the two materials. The Peltier coefficient is an empirically measured number that must be established for any material. Compact cooling devices have been constructed from such junctions to, for example, remove heat from electronic circuits. Typically, prior art cooling devices comprise a pair of junctions. If two such junctions are connected in series, but with opposite polarity, so that one common material serves as one side of both junctions, heat is absorbed by one junction and transferred through the common material to be discharged by the other junction. Hence, an effective heat pumping mechanism may be built to move heat energy between any two desired locations. The converse effect is also observed. If the two junctions are held at different temperatures, a voltage is produced across the series connected junctions. This is known as the Seebeck effect. The generated voltage is the Seebeck voltage. When the two materials forming the junctions cooperate to yield a large Peltier coefficient, a comparatively large Seebeck voltage is developed. The Seebeck coefficient of each material is equal to the Peltier coefficient multiplied by the absolute temperature. For simple metals, the Seebeck coefficient gets smaller at lower temperatures and approaches zero as the temperature approaches zero. The common material that forms one side of both junctions needs to have the right quantum mechanical characteristics to produce a large Seebeck coefficient. In addition, the material must conduct both the electric current and the e heat current. At the same time, the common material must have a low thermal conductivity so as to prevent thermal equilibrium between the hot junction and the cold. Still further, the common material must have a low electrical resistance to prevent ordinary joule heating, from the passage therethrough of the electric current, which heat could flow to the cold junction at a greater rate than the heat is removed from the junction by the Peltier effect. Clearly, the choice of materials is severely limited. The balancing of all the above thermal and electric factors is what defines an efficient thermoelectric cooler. Prior art thermoelectric coolers use doped narrow gap semiconductors for the common material and metals for the other side of the junctions. Because of the relative Fermi levels, only the most energetic electrons can cross the junction from the metal into the semiconductor. Hence, hot electrons are selectively withdrawn from the junction, cooling it. The hot electrons flow through the common semiconductor to and across the other junction, arriving in the metal with an energy considerably in excess of the Fermi energy. The excess energy is dissipated in collisions with the lattice in the metal, warming the second junction. Metal/narrow gap semiconductor junctions are preferred in the prior art, since for a certain temperature range they combine the best balance of strong Seebeck effect, not very high resistance, and low thermal conductivity, but such junctions do not perform well at very low temperatures. This results from the fact that semiconductor resistance rises exponentially with decreasing temperature so that joule heating becomes the dominant factor. Thus, despite the improvement in the Seebeck effect at lower temperatures, the prior art cooling devices are overwhelmed by resistive heating from the electric current. The present invention avoids this problem with new and novel junction materials that allow efficient operation at cryogenic temperatures.